1. Field of the invention
The present invention relates to a control device for smart card readers, a smart card reading activation device, and corresponding products.
2. Description of the Related Art
Set-top boxes (hereinafter noted “STBs”) are designed for different kinds of TV program reception and decoding. TV reception may be only analog, only digital, or analog and digital. In case of analog reception, the TV programs are generally not encrypted. As a consequence, the user is able to view the programs without having to pay special fees. In this case, the STBs need not be equipped with smart card interfaces allowing the TV program de-encryption.
In case of digital reception, the TV programs may be broadcast without any encryption, being then “free to air” programs, or be encrypted. In the latter case, a smart card interface is needed.
Depending on the TV program broadcast, it may also be necessary to pay for the selected TV program before being able to de-encrypt it. In this scenario, not only a typical de-encryption smart card interface is necessary, but usually also a “banking” smart card interface. The difference between “de-encryption” and “banking” smart card interface relates to the standard it has to comply with, which may impact on hardware (however, if an STB is equipped with two smart card readers, most of the time, they are designed with exactly the same hardware).
Set-top boxes have usually one or two smart card readers, allowing implementations as described below:                one de-encryption smart card reader,        or two de-encryption smart card readers, each one processing a different de-encryption process, which may notably consist in different standards (standards may be slot affected or not),        or one de-encryption smart card reader and one banking smart card reader.        
Above possibilities allow to respond to most common configurations that can be found on the STB market. However, the following configurations may appear and are not taken into account:                STB size is too small for a second smart card reader (it is the case for some new STB generations, which tend to decreasing sizes),        STB user may wish to de-encrypt user friendly more than two different encryption standards; namely, it would be desirable to avoid user operation for insertion of the relevant smart cards when zapping from one program to another, the cards being ideally always inserted in the corresponding smart card readers.        
A possible solution to solve those problems would consist in adding one or several external smart card readers, further to the STB including its own internal smart card readers. However, this would involve providing specific output connectors, one for each external smart card reader, and this would increase consequently the complexity of the control system, notably to activate and de-activate the relevant smart card readers for the current communications.
Document EP-0923246 concerns an interface for connecting one or more conditional access modules to a receiver. That interface includes interface sections, each for connection with a respective socket for receiving a conditional access module. Moreover, each interface section has input lines and output lines for connection to the corresponding socket. The interface sections are arranged in series, with the input lines of one interface section being connected to the output lines of the next interface section. Further, each interface section includes an electronically controllable switch connecting the output lines of that interface section to the input lines of the same interface section, such that each socket may be selectively bypassed when the associated conditional access module has not been connected.
Though that technique appears flexible in use, it requires some specific components, like tri-state buffers or special electronically controllable switches. Moreover, it is necessary to check systematically for each interface section if a conditional access module is present or not, which is processing consuming.
Document WO-00/59210 describes a system for interfacing multiple conditional access card modules. Several interface circuits of a conditional access unit provide access to respective cards. A central processor of that unit is coupled to the interface circuits to communicate with the card modules. The central processor determines which cards to address by extracting a code from service information in a received stream. Then, either it contacts selectively the targeted card module (in a non-specified way) or, when the card modules are connected in a daisy chain, it sends a same transport stream to all the series card modules (no selection is then done).
Thus, that prior art either does not provide selection of the card modules, or relies on multiple interfaces, one for each selectable card module.